For problems related to media (video/audio) -- especially when the reporter is not sure which area of the media stack the problem is in. This category will mostly be for untriaged video/audio issues. Bugs in this category will typically be moved to another media category during the triage process.

#content is in favour:
11:45 < reyre> Ms2ger: captions display, but none of the special layout
positioning for cues with regions is implemented
11:45 < Ms2ger> Oh
11:46 < Ms2ger> And we still implement a DOM API to change them, but that
doesn't do anything?
11:46 < reyre> yes
11:46 < Ms2ger> Disable the API :)
11:49 < sicking> rillian: yes, if the DOM API is a bunch of no-ops, then
definitely disable it.
Given the timing, I'd develop a patch against the aurora branch first and push it to try, then work on the nightly version.

This puts the DOM API behind a pref. The other part of this is having vtt.js only do layout for Cues, disregarding their Regions. Right now we don't have to do anything for this since vtt.js just does layout for Cues. However, if this pref is still around when we enable Region layout then we need to do something about that.
I've added a note on the relevant vtt.js issue for this and I think we should also keep this bug open to track it in Gecko. See https://github.com/mozilla/vtt.js/issues/267 for details.

(In reply to Ralph Giles (:rillian) on vacation until March 31 from comment #4)
> Does this work? It appears to only generate code to check the second pref.
That's strange because I tested it manually as well and turning them both on and off together/separately had the expected behaviour.
(In reply to Boris Zbarsky [:bz] from comment #7)
> Duplicate extended attributes are OK. Duplicate [Pref] annotations are not.
So is this a problem with codegen or with the way I've structured this? What's the best way to fix this?

To make it do what you want you need to fix the codegen to union the prefs. Sounds like bz maybe doesn't want that. I suppose you could just use webvtt.region.enabled pref only; the question is what breaks if you enable that but not webvtt.

> So is this a problem with codegen or with the way I've structured this?
The codegen problem is that it allows you to write IDL that then doesn't do what you'd think it does in this case.
If you want to check two separate prefs, use Func and check the prefs directly in the function. For one thing, the codegen has no way to tell whether you wanted to enable if both are true or if either one is true...

(In reply to Boris Zbarsky [:bz] from comment #11)
> If you want to check two separate prefs, use Func and check the prefs
> directly in the function. For one thing, the codegen has no way to tell
> whether you wanted to enable if both are true or if either one is true...
Thanks for the clarification Boris.
I've updated the VTTRegion.webidl so that it uses Func and checks the prefs directly.
Carrying forward r=rillian.